The present invention relates to a so-called xe2x80x9cturbocompoundxe2x80x9d internal combustion engine, in particular for an industrial vehicle.
xe2x80x9cTurbocompoundxe2x80x9d internal combustion engines are known, which comprise an auxiliary turbine downstream from the turbocharger turbine and connected mechanically to the drive shaft to recover and convert part of the residual energy of the exhaust gas into mechanical power for the drive shaft.
The auxiliary turbine and drive shaft are normally connected mechanically (here intended in the broader sense of the ability to transfer mechanical power, as opposed to a xe2x80x9crigid connectionxe2x80x9d) by a transmission comprising a gear reducer and a hydraulic joint permitting a certain amount of xe2x80x9cslippagexe2x80x9d. In the event of a breakdown of the hydraulic joint or relative hydraulic supply circuit, the auxiliary turbine may become mechanically disconnected from the drive shaft, and so unaffected by the braking torque produced by rotation of the drive shaft, so that the speed of the turbine, driven exclusively by the exhaust gas, may exceed the safety limit, thus resulting in breakdown of the turbine.
By way of a solution to the problem, turbocompound engines have been devised featuring a safety control device for detecting the oil pressure of the hydraulic joint, and which intervenes when the pressure falls below a predetermined limit. This type of device, however, is only effective and only intervenes in the case of hydraulic faults, whereas faults in the torque transmission of the hydraulic joint have been found to occur, for example, even when the system circuitry is sound but the oil particularly dirty.
It is an object of the present invention to provide a turbocompound internal combustion engine featuring an auxiliary turbine speed control device designed to eliminate the aforementioned drawbacks typically associated with known devices.
According to the present invention, there is provided a turbocompound internal combustion engine comprising a drive shaft; a turbocharger comprising a turbine and a compressor; an auxiliary turbine located along the path of the exhaust gas, downstream from said turbine of said turbocharger; and transmission means between said auxiliary turbine and said drive shaft; characterized by comprising a first angular speed sensor for detecting the rotation speed of said auxiliary turbine; and a control device for controlling the rotation speed of said auxiliary turbine, and which is connected to said first sensor and in turn comprises calculating means for calculating a range of permissible values of said rotation speed of said auxiliary turbine, comparing means for comparing the rotation speed of said auxiliary turbine measured by said first sensor with said range of permissible values, and control means for controlling operating parameters of the engine in response to an enabling signal generated by said comparing means, so as to maintain said speed of said auxiliary turbine within said range of permissible values.
The present invention also relates to a method of controlling a turbocompound internal combustion engine comprising a drive shaft; a turbocharger comprising a turbine and a compressor; an auxiliary turbine located along the path of the exhaust gas, downstream from said turbine of said turbocharger; and transmission means between said auxiliary turbine and said drive shaft; said method being characterized by comprising the steps of measuring the rotation speed of said auxiliary turbine by means of a sensor; calculating a range of permissible values of said rotation speed of said auxiliary turbine; comparing the rotation speed of said auxiliary turbine measured by said sensor with said range of permissible values; and controlling operating parameters of the engine in response to the outcome of said comparing step, so as to maintain said speed of said auxiliary turbine within said range of permissible values.